A Wireless Local Area Network (WLAN) typically comprises at least one Access Point (AP) and one or more WLAN devices, configured to communicate with and connect to the AP wirelessly. The AP then provides a network resource, such as the Internet, to each of the connected WLAN devices.
A commonly used form of WLAN is based on the IEEE 802.11 family of standards. The Wi-Fi Alliance trade association specifies the requirements for interoperability of APs and devices and certifies products meeting those requirements. Although each AP conventionally operates independently from other APs, networks of APs spread across a geographical area have been established, managed by a common network operator, to facilitate easier Internet access with high data rates.
Recent developments mean that APs and WLAN devices can support operation using multiple frequency bands. APs that are operated as part of a network may provide such support to allow operability with a range of different WLAN devices, some of which may support use of only a single frequency band or a small number of frequency bands. The AP transmits beacons using each of the frequency bands that it supports. A WLAN device can only receive the beacon transmitted using one frequency band at any one time to discover the existence of the AP. However, in first generation WLAN systems, the WLAN device may have no knowledge about whether the AP is part of a network, what functionality the AP supports and whether the WLAN device has subscription rights to access the AP prior to association with the Access Point. These features would only become apparent following connection to and authentication by the AP to enable association.
Developments in industry standards, such as IEEE 802.11u, seek to improve the accessibility of AP networks by WLAN devices. This is achieved by introducing new protocols which allow WLAN devices to communicate with an AP or a server of the AP network operator prior to association, than is prior to connection and authentication. The Generic Advertisement Service (GAS) allows link layer communication between a WLAN device and a server of the AP network operator via the AP. The Access Network Query Protocol (ANQP) is a query and response protocol (sometimes termed a pre-association protocol). Using ANQP, a WLAN device can determine basic information about the AP and network of APs that would otherwise have been unavailable prior to connection and authentication. These two protocols are intended to be used together for querying identified APs, thereby allowing the WLAN device to select an AP appropriately.
A challenge in the development of ANQP is ensuring that the WEAN device is provided with useful information about an AP, whilst minimising redundant information that wastes capacity and reduces efficiency. It is therefore desirable that ANQP is limited only to information that the WLAN device can use beneficially in selecting an AP appropriately.